In 1981, Scottish geologist Douglas Dixon wrote a book about what creatures may evolve to look like 50 million years from now post humans. The book entitled entitled After Man, came with drawings of biomorphs to illustrate his vision.
Check out the ‘flunkey' above, a flying monkey that glides like a squirrel.
From Evolution After Humans:
Imagine a game of biogeographical musical chairs in which penguins have evolved comb-like beaks to sieve plankton as whales do, rats have replaced the big cats as dominant carnivores, cats swing through the tropical canopy chasing monkeys, and monkeys glide on flaps of skin like flying squirrels. The book’s central idea is convergent evolution: that similar traits arise independently in different species, to perform similar functions in similar environments.